The VCC_BATT pin of the Colibri modules is used to power the module's internal RTC. The VCC_BATT pin must be connected to a 3.3V source. If voltage is not supplied by a battery, then the pin must be connected to another 3.3V source even if the RTC is not required.
Note: This is in contrast to the Apalis modules which don't require power to be applied on the VCC_BACKUP pin if the RTC is not required.
Below is an example of how to supply the VCC_BATT pin with either voltage source:
Some modules provide battery charging functionality. Therefore, when using a single non-rechargeable voltage source, the inline diode and resistor will still be required to protect the supply from reverse current. A FET may also be used for reverse current protection. Take care to ensure the circuit's reverse leakage current is low enough for safe operation with the chosen battery/power supply. High quality and/or redundant diodes should be used to safeguard against component failure which could result in battery fire/explosion.
More information regarding the use of a backup battery is provided at the following page: Backup battery.